Yes, an ML-Class diesel would be plain daft for that type of use. And, of course, isn't EU6. Because before the demonisation of diesel and before EU6, diesels made more sense than petrols for big SUVs because they made the fuel costs affordable, that's why almost all of them were diesel. The tide is only just turning and manufacturers are only just starting to install petrol engines and petrol hybrid drivetrains in SUVs. Your best bet is probably a RAV4 hybrid, an RX450h or an Outlander PHEV.